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Performance of a deep excavation and the influence on adjacent piles:A case history in karst region covered by clay and sand

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Underground Space 2023年第1期8卷 45-60页

作者： Yubing Yang Caiyuan Chen Chao Liu Longtian Huang Wei Chen Nengyou Lin Jie Cui Wandong Xie College of Water Conservancy and Civil Engineering South China Agricultural UniversityGuangzhou 510642PR China School of Civil Engineering Guangzhou UniversityGuangzhou 510006PR China Architectural Design and Research Institute of Guangdong Province Guangzhou 510010PR China CCCC–FHDI Engineering Co. LtdGuangzhou 510290PR China

This paper presents a case study of deep excavation adjacent to an existing bridge in karst region of Guangzhou city,*** movements of retaining structures,settlements of surrounding ground and pipelines,and the responses of bridge piles were measured and evaluated.A sudden surge of groundwater was recorded at the north pit when excavated ***-cement columns using the Metro Jet System(MJS)method was employed along the outer perimeters of the diaphragm wall where water inflow occurred,for the sake of blocking the flow *** measured maximum wall deflection dhm in this case ranged from 0.13%H to 0.3%H,with a mean value of 0.2%H(H is the excavation depth),which agreed well with the empirical prediction in mixed *** the MJS treatment,the wall and surrounding soils experienced notable lateral deflection and *** bridge piles experienced significant settlement since the excavation commenced,which might be attributed to the inherent deficiency in geological condition and pile *** soil disturbance induced by the adjacent deep excavation accelerated bridge *** finite element analysis revealed that the excessive settlement of the bridge piles and ground surface resulted from confined-water withdrawal in sand layers.

关键词： deep excavation MJS treatment Pile-foundation Karst region Confined-water

Predicting the strut forces of the steel supporting structure of deep excavation considering various factors by machine learning methods

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Underground Space 2024年第5期18卷 114-129页

作者： Haibo Hu Xunjian Hu Xiaonan Gong Research Center of Coastal and Urban Geotechnical Engineering Zhejiang UniversityHangzhou 310058China

The application of steel strut force servo systems in deep excavation engineering is not widespread,and there is a notable scarcity of in-situ measured *** presents a significant research gap in the *** this,our study introduces a valuable dataset and application scenarios,serving as a reference point for future *** main objective of this study is to use machine learning(ML)methods for accurately predicting strut forces in steel supporting structures,a crucial aspect for the safety and stability of deep excavation *** employed five different ML methods:radial basis function neural network(RBFNN),back propagation neural network(BPNN),K-Nearest Neighbor(KNN),support vector machine(SVM),and random forest(RF),utilizing a dataset of 2208 measured *** points included one output parameter(strut forces)and seven input parameters(vertical position of strut,plane position of strut,time,temperature,unit weight,cohesion,and internal frictional angle).The effectiveness of these methods was assessed using root mean square error(RMSE),correlation coefficient(R),and mean absolute error(MAE).Our findings indicate that the BPNN method outperforms others,with RMSE,R,and MAE values of 72.1 kN,0.9931,and 57.4 kN,respectively,on the testing *** study underscores the potential of ML methods in precisely predicting strut forces in deep excavation engineering,contributing to enhanced safety measures and project planning.

关键词： deep excavation Steel supporting structure Strut forces Machine learning Time Temperature

A modified back analysis method for deep excavation with multi-objective optimization procedure

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第4期16卷 1373-1387页

作者： Chenyang Zhao Le Chen Pengpeng Ni Wenjun Xia Bin Wang State Key Laboratory of Geomechanics and Geotechnical Engineering Institute of Rock and Soil MechanicsChinese Academy of SciencesWuhan430071China Guangdong Research Center for Underground Space Exploitation Technology School of Civil EngineeringSun Yat-sen UniversityGuangzhou510275China Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) Zhuhai519000China Jiangsu Provincial Transportation Engineering Construction Bureau Nanjing210004China

Real-time prediction of excavation-induced displacement of retaining pile during the deep excavation process is crucial for construction *** paper proposes a modified back analysis method with multi-objective optimization procedure,which enables a real-time prediction of horizontal displacement of retaining pile during *** opposed to the traditional stage-by-stage back analysis,time series monitoring data till the current excavation stage are utilized to form a multi-objective ***,the multi-objective particle swarm optimization (MOPSO) algorithm is applied for parameter *** optimized model parameters are immediately adopted to predict the excavation-induced pile deformation in the continuous construction *** achieve efficient parameter optimization and real-time prediction of system behavior,the back propagation neural network (BPNN) is established to substitute the finite element model,which is further implemented together with MOPSO for automatic *** proposed approach is applied in the Taihu tunnel excavation project,where the effectiveness of the method is demonstrated via the comparisons with the site monitoring *** method is reliable with a prediction accuracy of more than 90%.Moreover,different optimization algorithms,including non-dominated sorting genetic algorithm (NSGA-II),Pareto Envelope-based Selection Algorithm II (PESA-II) and MOPSO,are compared,and their influences on the prediction accuracy at different excavation stages are *** results show that MOPSO has the best performance for high dimensional optimization task.

关键词： Multi-objective optimization Back analysis Surrogate model Multi-objective particle swarm optimization(MOPSO) deep excavation

Lessons learnt from a deep excavation for future application of the observational method

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第3期10卷 468-485页

作者： Raul Fuentes Anton Pillai Pedro Ferreira School of Civil Engineering University of LeedsLeedsLS2 9JTUK Ove Arup and Partners 13 Fitzroy StreetLondonW1T 4BQUK Department of Civil Environmental&Geomatic EngineeringUniversity College LondonChadwick BuildingGower StreetLondonWC1E 6BTUK

This paper draws lessons learnt from a comprehensive case study in overconsolidated clay. Apart from the introduction of the case study, including field measurements, the paper draws on the observations and a three-dimensional（3 D） numerical analysis to discuss the implications of observations in the application of the observational method（OM） in the context of the requirements of EUROCODE 7（EC7）.In particular, we focus on corner effects and time-dependent movements and provide initial guidance on how these could be considered. Additionally, we present the validation of a new set of parameters to check that it provides a satisfactory compliance with EC7 as a set of design parameters. All these findings and recommendations are particularly important for those who want to use the OM in similar future projects.

关键词： deep excavation Basement Ground movements Wall movements Retaining wall Corner effects Time-dependent movements

A case study on behaviors of composite soil nailed wall with bored piles in a deep excavation

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Journal of Central South University 2013年第7期20卷 2017-2024页

作者： ZHU Feng-bin MIAO Lin-chang GU Huan-da CHENG Yue-hong Institute of Geotechnical Engineering Southeast University Nanjing 210096 China School of Civil Engineering Suzhou University of Science and Technology Suzhou 215011 China Sttzhou Erjian Construction Group Co. Ltd Suzhou 215131 China

A complete case of a deep excavation was explored. According to the practical working conditions, a 3D non-linear finite element procedure is used to simulate a deep excavation supported by the composite soil nailed wall with bored piles in soft soil. The modified cam clay model is employed as the constitutive relationship of the soil in the numerical simulation. Results from the numerical analysis are fitted well with the field data, which indicate that the research approach used is reliable. Based on the field data and numerical results of the deep excavation supported by four different patterns of the composite soil nailed wall, the significant corner effect is founded in the 3D deep excavation. If bored piles or soil anchors are considered in the composite soil nailed wall, they are beneficial to decreasing deformations and internal forces of bored piles, cement mixing piles, soil anchors, soil nailings and soil around the deep excavation. Besides, the effects due to bored piles are more significant than those deduced from soil anchors. All mentioned above prove that the composite soil nailed wall with bored piles is feasible in the deep excavation.

关键词： deep excavation 3D non-linear finite element bored pile composite soil nailed wall corner effect deformation internal force

Case study of post uplift in deep excavation of a subway station in thick soft clay using long pile foundations

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Underground Space 2022年第2期7卷 254-267页

作者： Yanbin Gao Zhouxiang Ding Department of Geotechnical Engineering Tongji University#1239 Siping RoadShanghai 200092China Department of Mechanical Engineering University of SaskatchewanCanada

There is growing engineering concern about the base heave and post uplift phenomena in deep excavation in soft clay,which may pose a risk of instability of retaining *** purpose here is to conduct a detailed case study on the post uplift observed in a 17.6-meterdeep braced excavation of a subway station in thick soft clay(total thickness up to 42 m)in *** this case,a large uplift up to 87 mm unexpectedly developed for the post founded on a 30-meter-long pile *** were first made to examine the complex relationships between the post uplift with the excavation depth(H),Terzaghi’s safety factor against base heave(Fs)and maximum deflection of retaining wall.A simplified approach for soil-post-strut interaction analysis was then proposed and used for quantitative *** working characteristics of the long pile foundation under low safety factor against base heave(Fsdeep soil movement below the neutral plane results in the observed post uplift;(c)strut reaction plays a minor role in the restriction of post *** influence of base treatment and excavation/construction procedures on post uplift and the principles of pile foundation design are also discussed in this paper.

关键词： Post uplift deep excavation Field observations Neutral plane Soft clay Pile foundation

Numerical analysis on zone-divided deep excavation in soft clays using a new small strain elasto–plastic constitutive model

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Underground Space 2022年第1期7卷 19-36页

作者： Afnan Younis Tanoli Bin Yan Yong-lin Xiong Guan-lin Ye Usama Khalid Zhong-hua Xu Department of Civil Engineering State Key Laboratory of Ocean Engineering and ShanghaiKey Laboratory for Digital Maintenance of Buildings and InfrastructureShanghai Jiao Tong UniversityShanghai 200240China Institute of Geotechnical Engineering Ningbo UniversityNingbo 315211China Department of Civil Engineering Khwaja Fareed University of Engineering and Information TechnologyRahim Yar Khan 64200Pakistan East China Architectural Design&Research Institute Shanghai 200002China

Accurate prediction of displacements associated with deep excavations is essential to ensure safety and stability of the excavation and to prevent any damage and distress to the adjoining *** paper presents a numerical approach for prediction of ground displacements related to a zone-divided deep excavation construction executed in Shanghai soft clays based on a new elasto–plastic con-stitutive model(small-strain Shanghai model)that incorporates small strain *** model can describe the mechanical properties and structural and over-consolidated characteristics of natural *** model is implemented into a finite element analysis *** analysis on the deep excavation in Shanghai using zone-divided method is conducted.A comparison between monitored and simulated results of horizontal displacements along the diaphragm wall,the settlements in the surroundings,and the effects on the adjoin-ing metro tunnel due to excavation construction is carried *** attention is paid to the stiffness degradation of representative elements in the *** simulated displacements show a good agreement with the monitored ***,this study provides an integrated solution for predicting displacements related to deep excavation in soft clays.

关键词： deep excavation Soft clays Small strain Elasto-plastic model Ground displacements Metro tunnels

Performance and environmental impacts of deep foundation excavation in soft soils:A field and modeling-based case study in Nanjing,China

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Underground Space 2024年第5期18卷 218-238页

作者： Chenhe Ge Meng Yang Pengfei Li Mingju Zhang Zhonghao Zhang Key Laboratory of Urban Security and Disaster Engineering Ministry of EducationBeijing University of TechnologyBeijing 100124China China Construction Second Engineering Bureau Ltd. Beijing 100070China The Third Construction Engineering Company Ltd.of China Construction Second Engineering Bureau Beijing 100070China

This paper focuses on the performance of a braced deep excavation in soft soil based on field monitoring and numerical *** tests were conducted to determine the soil parameters used in the modified Cam–Clay(MCC)*** field monitoring means were adopted and a three-dimensional model was *** and temporal effects induced by the excavation are investigated for the deep-large foundation pit in soft *** characteristics of the enclosure structure and the surrounding environment throughout the excavation process are *** behaviors of diaphragm walls,columns,the maximum wall deflection rate,ground surface settlement,and utility pipelines were focused on and investigated during the whole excavation ***,the axial forces of the internal supports are *** on the measured and simulated data,the following main conclusions were obtained:the numerical simulation results are in good agreement with the measured values,which proves the accuracy of the model parameters;the wall and the ground surface showed the maximum displacement increment at stage 9,which was a coupled product of the"creep effect"of the soft soil in Nanjing,China and the"depth effect"of the excavation;as the excavation progressed,the ground settlement changed from a"rising"to a"spoon-shaped"trend,dvm was measured betweenδ_(vm)=0.0686%H andδ_(vm)=0.1488%H;the rebound deformation curve of the pit bottom was corrugated,and the depth of disturbance of the pit bottom after the completion of soil unloading was 2–3 times the excavation depth;the closer the pipeline is to the corner of the pit,the less the excavation process will affect the settlement of the pipeline and the less the obvious pit corner effect will occur;the support strength of the buttress and the longest corner brace should be strengthened during the actual construction process to ensure the stability of the foundation deformation.

关键词： deep excavation Modified Cam-Clay Deformation characteristics Creep effect Corner effect

A post-peak dilatancy model for soft rock and its application in deep tunnel excavation

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第3期15卷 683-701页

作者： Wuqiang Cai Hehua Zhu Wenhao Liang Xiaojun Wang Chenlong Su Xiangyang Wei Department of Geotechnical Engineering College of Civil EngineeringTongji UniversityShanghai200092China State Key Laboratory for Disaster Reduction in Civil Engineering Tongji UniversityShanghai200092China China Railway Construction Co. Ltd.Beijing100855China

The dilation angle is the most commonly used parameter to study nonlinear post-peak dilatancy(PPD)behavior and simulate surrounding rock deformation;however,simplified or constant dilatancy models are often used in numerical calculations owing to their simple mathematical *** study developed a PPD model for rocks(rock masses)based on the Alejanoe-Alonso(A-A)dilatancy *** developed model comprehensively reflects the influences of confining pressure(σ_(3))and plastic shear strain(γ^(p)),with the advantages of a simple mathematical form,while requiring fewer parameters and demonstrating a clear physical *** overall fitting accuracy of the PPD model for 11 different rocks was found to be higher than that of the A-A model,particularly for Witwatersrand quartzite and jointed *** applicability and reliability of the PPD model to jointed granites and different scaled Moura coals were also investigated,and the model was found to be more suitable for the soft and large-scale rocks,*** rock *** PPD model was also successfully applied in studying the mechanical response of a circular tunnel excavated in strain-softening rock mass,and the developed semi-analytical solution was compared and verified with existing analytical *** sensitivities of the rock dilatancy to γ^(p) and σ_(3) showed significant spatial variabilities along the radial direction of the surrounding rock,and the dilation angle did not exhibit a monotonical increasing or decreasing law from the elasticeplastic boundary to the tunnel wall,thereby presenting the σ3-or γ^(p)-dominated differential effects of rock *** deformation parabolically or exponentially increased with increasing in situ stress(buried depth).The developed PPD model is promising to conduct refined numerical and analytical analyses for deep tunneling,which produces extensive plastic deformation and exhibits significant nonlinear post-peak behavior.

关键词： deep excavation Post-peak dilatancy(PPD)model AlejanoeAlonso(AeA)dilatancy model Soft rock